Study finds attack ads from the 2008 presidential campaign appeared to show Obama with darker-than-usual skin — these are the ads

Screenshot from a 2008 advertisement supporting Republican presidential candidate John McCain. Museum of the Moving Image A study by Stanford University researchers that analyzed more than 100 ads from the 2008 US presidential election has found that Sen. John McCain's (R-Arizona) campaign used images of then-Senator Barack Obama (D-Illinois) that made his skin appear darker than usual.

The study, published in the academic journal Public Opinion Quarterly in December, suggests that the images could have been intended to tap into possible racial biases of some viewers.

"Ads that portray black candidates with a darker complexion might prime negative stereotypes about blacks, damaging the candidate's election prospects in a way that has nothing to do with political fitness for office and is difficult to detect," the researchers wrote in the study.

In the GOP field, where real-estate mogul and current front-runner, Donald Trump has consistently led in the polls, the candidate's controversial approach to matters of immigration, homeland security, and civil rights has relied on similar methods for attacking minority groups.

In 2008, the depictions of Obama's skin tone varied throughout the campaign season, but he appeared especially dark-skinned in Republican attack ads that aired closer to election day, according to the Stanford study.

Meanwhile, McCain's skin appeared gradually lighter over time in the same ads.

Former Republican Vice Presidential candidate Gov. Sarah Palin (R-Alaska) and former GOP presidential candidate Sen. John McCain (R-Arizona). AP The disparity in skin tone is not necessarily a result of deliberate manipulation by the McCain campaign. The researchers noted that "more shadowed" images of Obama may have been selected to match the sinister tone of the attack ads.

According to the study, Obama's skin appeared the darkest in ads connecting him to crime, including ones that attempted to link the candidate to Bill Ayers, the former leader of the radical left-wing organization Weather Underground:

Another ad sought to tie Obama to alleged misconduct committed by the Association of Community Organizations for Reform Now, known by the acronym ACORN:

Other GOP attack ads in question paint Obama as disrespectful ...

... and irresponsible ...

In another portion of the study, researchers showed participants images that depicted Obama with a lighter or darker-than-usual skin tone. The images were manipulated accordingly for the purposes of the study.

The researchers found participants were quicker to think of negative black stereotypes — such as laziness and criminal behavior, for example — after seeing the darker-skinned version.

The findings give new ammunition to critics who claim the Republican Party may use implicit racial appeals to attract some voters.

Manipulated images of Barack Obama that were used by researchers in the study. Public Opinion Quarterly "When you blacken somebody's skin, you're doing it for only one reason. It's to make them look darker and more sinister," First Amendment attorney Daniel Barr told Arizona's KTVK-3 TV.